湿热环境下FRP-混凝土界面的疲劳粘结-滑移机理研究

It is well known that the bridge structures in sub-tropical coastal regions such as south China are subjected to high temperature and humidity and vehicle loading as well; the durability of the CFRP-strengthened bridge structures in such regions is a significant/fundamental issue not well understood. This project is proposed to study the bond-slip mechanism of the FRP-concrete bonded interfaces (referred to as interface for brevity next) subjected to the combined effects of hygrothermal environment and vehicle loadings. In first stage of this study, in order to solve the main experimental problems such as ensuring the pure shear stress state of the interface during loading, accurately measuring the slip of the interface, and effectively obtaining test data during descending stage of the bond-slip curves, an optimized shear testing method will be proposed to study the bond behaviors of the interfaces subjected to fatigue loading under the hygrothermal environment in which the non-contact on-line high precision measurement methods will be deployed to study the full-range damage process of the interface. Then a bond-slip model will be developed to accurately describe the experimental bond-slip curves of the interfaces subjected to fatigue loading under the hygrothermal environment, overcoming the mechanical and mathematical difficulties in quantitatively describing descending stage of the bond-slip curves. Based on the research results from this study, the bond-slip mechanism of the interface subjected to the combined effects of hygrothermal environment and vehicle loadings can be preliminarily clarified, providing theoretical and experimental supports/bases to the durability assessment and design of the CFRP strengthened bridge structures, especially in the sub-tropical coastal regions.

针对我国南方及沿海地区的典型气候以及公路桥梁的活载特点，探讨碳纤维增强复合材料（CFRP）加固混凝土桥梁结构耐久性的基础科学问题——FRP-混凝土界面在湿热环境与车辆荷载共同作用下的疲劳粘结-滑移机理。提出湿热环境下CFRP-混凝土界面的剪切疲劳实验方法、CFRP-混凝土界面疲劳损伤全过程的非接触式在线高精度测试方法，以解决剪切疲劳实验过程如何保持界面处于纯剪切应力状态、界面滑移量的精确测量方法和技术、界面粘结-滑移实验曲线下降段数据的有效获取等关键技术；建立考虑湿热环境影响的CFRP-混凝土界面的疲劳粘结-滑移模型，以准确描述界面粘结-滑移实验全曲线，突破现有FRP-混凝土界面粘结-滑移实验曲线下降段的力学-数学描述难题；初步探明CFRP-混凝土界面在湿热环境与疲劳荷载共同作用下的粘结-滑移机理，为CFRP加固混凝土桥梁结构的耐久性评估和加固设计提供理论依据和基础实验数据。

对于我国南方及沿海地区的FRP加固钢筋混凝土（RC）桥梁结构，湿热的大气环境和车辆疲劳荷载共同作用会加速界面粘结性能的退化，发生疲劳破坏，直接影响加固桥梁结构的整体性和安全性，因此，探讨FRP-混凝土界面在湿热环境和疲劳荷载作用下的粘结-滑移机理具有重要的科学意义。.本项目以碳纤维薄板（Carbon Fiber Laminate，简称CFL）与混凝土的粘结界面为研究对象，考虑我国南方湿热的大气环境，对湿热环境和疲劳荷载作用下CFL-混凝土界面的粘结滑移机理进行了研究，主要研究内容和结论如下：.（1）提出了FRP-混凝土界面的剪切疲劳实验方法。研制了装夹具，确保CFRP-混凝土界面在疲劳实验过程中始终处于纯剪切应力状态；研制了湿热环境和疲劳荷载共同作用的控制系统，实现加载条件；利用数字图像测试技术（Digital Image Correlation，DIC）非接触式精确测试方法，观测裂纹在疲劳荷载下的萌生、发展过程。.（2）湿热环境与疲劳荷载的非共同作用、共同作用的CFRP-混凝土界面粘结-滑移机理的实验研究。对双剪试件进行湿热环境预处理，然后在室温大气中实施疲劳实验，探讨了不同温度、湿度条件等对CFRP-混凝土界面粘结-滑移机理的影响。模拟CFRP加固混凝土桥梁结构的实际工作条件，在湿热环境箱内进行疲劳实验，探讨湿热环境和疲劳荷载共同作用下对界面粘结性能的加速退化机理。.（3）湿热环境与疲劳荷载下CFRP-混凝土界面的粘结-滑移模型研究。对CFRP-混凝土界面的粘结-滑移实验曲线进行分析，构建考虑湿热环境的界面疲劳粘结-滑移模型，提出模型中特征参数的表达式。.本项目的研究结果将为FRP-混凝土界面在湿热环境下的疲劳性能研究提供方法参考意义，为CFRP加固RC结构的界面粘结-滑移耐久性分析提供理论依据和基础实验数据。.